RT-PCR Differentiation,Molecular And Pathological Characterization Of Andean And Ordinary Strains Of Potato Virus S In Potatoes In China

Potato (Solanum tuberosum L.) is the world’s fourth largest staple crop after rice, wheat and corn, and China is the largest potato grower and producer in the world. The development of potato industry has been threatened by a variety of viral pathogans. Potato virus S (PVS), is one of the most common viruses infecting potato crops worldwide. A survey of potatoes in a field in Hubei, China, revealed that PVS was the most abundant virus in this area, and an investigation into the molecular and pathological properties of this virus was warranted.To unveil the strain identity of the virus, primers specific to the ordinary and/or the Andean strains of PVS (i.e, PVSO and PVSA) were designed. RT-PCR using these primers successfully detected PVSO and PVSA in the samples. Sequence analysis of the amplicons confirmed the correctness of the RT-PCR assay. Two isolates, PVS HB24 and PVS HB7, representing PVSO and PVSA, respectively, were chosen for molecular and biological characterization. Both isolates contained a genome of 8,453 nt in length with six open reading frames. They shared a sequence identity of 79.5% at the complete genome sequence level. Phylogenetic analysis placed PVS HB24 and PVS HB7 to PVSO and PVSA clades, respectively. PVS HB24 induced chlorotic necrosis on the inoculated leaves but no visible symptom on the upper uninoculated leaves of Chenopodium quinoa after mechanical inoculation, whereas PVS HB7 induced both local and systemic symptoms on C. quinoa. ELISA and RT-PCR confirmed that PVS HB7 infected C. quinoa systemically whereas PVS HB24 failed to do so. Both isolates infected potato cv. Shepody and Solanum chacoense asymptomatically, but did not infect Nicotiana occidentalis and N. tobaccum cv. Samsun.This study was the first report of PVS strain status in China, and unveil the molecular and pathological properties of the first Chinese isolate of Andean strain of PVS. Moreover, a novel RT-PCR based method for PVS strain differentiation was developed, provide us a more efficient and time-saving option comparing with the biological and serological assay.